Roof bows are attached to vehicle roof structures to strengthen the roof assembly and support the roof rails and roof panel. Roof support pillars are typically located between the windows and doors of a vehicle. Roof support pillars are frequently identified as A, B, C and in some instances D-Pillars depending on the vehicle style. A B-Pillar is generally located immediately behind the front door of a vehicle and is traditionally used to mount the rear door hinges and associated rear doors. The B-Pillar often plays an important role in determining roof strength and the degree of side impact intrusion.
Vehicles often include moonroofs and sunroofs. In these vehicle, the B-Pillar roof bow typically omitted. Such vehicles must still adhere to certain strength requirements and moonroof assemblies must make up for the lack of support caused by the missing B-Pillar roof bow.